Add multi-resolution playback support

frontend/lib/providers/settings_provider.dart

@@ -62,12 +62,26 @@ class SettingsProvider with ChangeNotifier {
     return "rtmp://${uri.host}:1935/live";
   }
 
-  String playbackUrl(String roomId) {
+  String playbackUrl(String roomId, {String? quality}) {
     final uri = Uri.parse(_baseUrl);
+    final normalizedQuality = quality?.trim().toLowerCase();
+
     if (kIsWeb) {
-      return uri.replace(path: '/live/$roomId').toString();
+      return uri
+          .replace(
+            path: '/live/$roomId',
+            queryParameters:
+                normalizedQuality == null || normalizedQuality.isEmpty
+                ? null
+                : {'quality': normalizedQuality},
+          )
+          .toString();
     }
-    return "$rtmpUrl/$roomId";
+
+    if (normalizedQuality == null || normalizedQuality.isEmpty) {
+      return "$rtmpUrl/$roomId";
+    }
+    return "$rtmpUrl/$roomId/$normalizedQuality";
   }
 
   ThemeMode _themeModeFromString(String value) {